The present invention relates to an apparatus for detecting seated condition whether a human body is seated, and especially relates to an apparatus for detecting the seated condition utilizing an electrostatic capacity sensor.
Conventional apparatus for detecting seated condition utilizes an electrostatic capacity sensor. The electrostatic capacity sensor is used because it is superior in the stable output among other noncontacting sensors and it can accurately measure the very fine change. Further, antenna electrodes that are probes of the electrostatic capacity sensor can be changed their shapes and made smaller, so that if the antenna electrodes are provided in the inside of the seat, a person who sits on the seat does not feel them.
The apparatus for detecting seated condition is used in an automobile. Generally, in case of emergency, an airbag inflates between passenger and a body of the automobile to reduce the impact to be received by the passenger. The airbag apparatus requires to detect the passenger""s seated position accurately to control the operation of the airbag appropriately in all cases of the seated positions.
Therefore, in order to detect the seated condition of the passenger in the automobile, the antenna electrodes of the electrostatic capacity sensor are provided in the inside of the seat.
In the apparatus, the electrostatic capacity existing between the antenna electrodes and the body of the automobile is detected, and the seated condition is determined based on the detected result.
It is an object of the present invention to provide an apparatus for detecting seated condition whether a human body is seated, which can accurately detect the seated condition under any circumstances.
In order to achieve the above object, an apparatus for detecting seated condition of the present invention comprises an antenna electrode provided in the inside a seat, a power supply for supplying power for generating radio wave to the antenna electrode so that an electric field generates between the antenna electrode and a ground to detect a passenger on the seat, a detecting unit for detecting electrostatic capacity existing between the antenna electrode and the ground, and a data processing unit for determining the seated condition for the seat based on the detected electrostatic capacity. In this apparatus, the detecting unit detects a first value of the electrostatic capacity in a case that a passenger is not seated and a second value of the electrostatic capacity in a case that a passenger is seated. Then, the data processing unit corrects the second value of the electrostatic capacity based on the first value.
According to the apparatus for detecting seated condition of the present invention, the first output of the electrostatic capacity sensor in the case that the passenger is not seated is detected, and the second output of the electrostatic capacity sensor in the case that the passenger is seated is corrected based on the first output, so that the apparatus can accurately determine whether the passenger is seated under any circumstances.
Another noncontacting sensor can be provided in the apparatus for detecting seated condition. In this case, the accuracy for the detection of the passenger on the seated is further enhanced.
An apparatus for detecting seated condition of the present invention may comprise an antenna electrode provided inside a seat, a power supply for supplying power for generating radio wave to the antenna electrode so that an electric field generates between the antenna electrode and a ground to detect the passenger on the seat, a detecting unit for detecting electrostatic capacity existing between the antenna electrode and the ground, a data processing unit for determining the seated condition for the seat based on the detected electrostatic capacity, and a load sensor for detecting a load acting on the seat. In this case, the data processing unit determines the seated condition for the seat based on the detected value of the electrostatic capacity and a detected value of the load sensor. The electrostatic capacity, the weight and the center of gravity of the load detected by the load a sensor are premeasured for kinds of the seated posture, kinds of the passenger""s physique and kinds of loads, and the premeasured data are stored in the data processing unit as parameters, and the data processing unit determines the seated condition for the seat by comparing the detected value of the electrostatic capacity and the detected value of the load sensor with the parameters.
According to the apparatus for detecting seated condition, it can accurately detects the seated condition for the seat, e.g., whether the adult or child is seated, whether the subject on the seat is a passenger or a baggage and whether the passenger is seated.
Because the parameters are used, the detecting speed is increased.